. The biology of the Protozoa. Protozoa; Protozoa. 130 BIOLOGY OF THE PROTOZOA of silica are deposited in the inner protoplasm and passed out during reproduction to be cemented on the chitinous membrane in regular patterns (Euglypha alreolata. Fig. S, p. 30). Foreign bodies caught up in the wrinkles of withdrawing pseudopodia are similarly stored in the protoplasm to be used for shell-building purposes, Verworn, for example, compelling Difflugia to build its shell of difl'erent kinds of powdered glass. The lime shells of Foraminifera are formed in quite a different manner. Here, calcium carbon
. The biology of the Protozoa. Protozoa; Protozoa. 130 BIOLOGY OF THE PROTOZOA of silica are deposited in the inner protoplasm and passed out during reproduction to be cemented on the chitinous membrane in regular patterns (Euglypha alreolata. Fig. S, p. 30). Foreign bodies caught up in the wrinkles of withdrawing pseudopodia are similarly stored in the protoplasm to be used for shell-building purposes, Verworn, for example, compelling Difflugia to build its shell of difl'erent kinds of powdered glass. The lime shells of Foraminifera are formed in quite a different manner. Here, calcium carbonate is precipitated between two lam- ella? of chitin very much as a cement wall is made between board surfaces. Except for a single mouth opening such limestone shells may form an unbroken wall about the organism (imperforata) or. f Fig. 66.—A complex polythalamous shell of Opcrcidina (achematic). The shell is represented as cut in different planes to show the distribution of the canals and the arrangement of septa and chambers. (After Carpenter.) they may be perforated by myriads of minute pores (foramina) through which the pseudopodia pass to the outside, a condition which gave rise to the name Foraminifera. In the more compli- cated types of these limestone shells, which may reach a diameter of 2 or 3 inches, the calcium carbonate may be deposited at successive intervals of growth, thus giving rise to chambered structure of the cells. Such polythalamous shells are complicated by the presence of an intricate system of canals which, in life, are filled by moving protoplasm (Fig. 60). Skeletons of Heliozoaand Radiolaria, unlike the more clumsy shells of the Foraminifera, are usually delicate in structure and graceful in design. They are formed for the most part by a deposit of silica upon a chitinous base. Dreyer has given evidence to indicate that. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - col
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Keywords: ., bookauthorcalkinsgaryngarynatha, bookcentury1900, bookdecade1920
